On the flip side, there have been lots of college starters that projected to be top-of-the-rotation guys that failed to pan out. Appel, Miller, Matusz, et al. Jury is still out with Gray, Cole and Gausman. I'm not sure the data are stronger one direction or the other.
Fortunately, the Twins still have several months to collect more information on these players. I'm definitely not a draft historian, but it certainly seems from what I've read that Greene is on a different level than most former top HS pitchers. He is way more athletic than Kolek, and it sounds like he has a lot more velocity than guys like Stewart, Aiken. In fact, I'm not sure even Giolito and Taillon regularly reached triple-digits. Anyway, I'd love to see a long-time draft guru (like Law or Callis, for example) write a post comparing/contrasting Greene to other top HS pitchers.
Sure, college picks are risky too, or teams would never take high schoolers. The 2006 draft is a good example, it went (position added for potentially unfamiliar names):
Greg Reynolds (college RHP)
Billy Rowell (HS 3B)
So, not only was the best pitcher taken 7th overall out of high school, but the college picks didn't exactly pan out in the order selected, either. So really it comes down to some combination of performing the right scouting/analysis and getting lucky.
My point is just that, if Greene offers a little extra potential but one of the college guys is right there with him, plus 2-3 years closer to MLB, I want the guy that's closer and has thrown more innings in a season without breaking down.
I definitely do not want Brad Lincoln. But if there's a college guy with power stuff + command . . .